Occupancy sensing uses data collected from sensors to derive occupancy information for particular areas of a building, including which areas of the building are occupied, how many occupants there are, and who the occupants are. Occupancy sensing can be utilized by a broad range of applications, such as building automation systems and public safety systems, to improve quality or to add new functionality. For some of these applications, occupancy sensing can be added for little cost and can provide a high financial return. For example, according to the U.S. Department of Energy, commercial buildings accounted for 19% of the total energy consumption in the U.S. in 2010. Occupancy sensing can be deployed in these commercial buildings by leveraging existing network and information technology (IT) assets to reduce energy consumption, and thereby reduce utilities costs while also providing environmental benefits.
Typical commercial office buildings use static scheduling policies in their building automation systems, which usually make worst-case assumptions about occupancy. For example, a building can have a policy of turning on the heating, ventilation and air conditioning (HVAC) system and lights from 5:00 a.m. to 8:00 p.m. during weekdays. However, most employees are in the office from 9:00 a.m. to 5:00 p.m. If the building automation system is enhanced with occupancy sensing, then the HVAC system and lights could be turned off in these offices from 5:00 a.m. to 9:00 a.m. and from 5:00 p.m. to 8:00 p.m., resulting in significant energy savings.
The most common occupancy sensors found in the market are motion sensors, which use passive infrared (PIR) to detect whether someone is moving in an area. However, there are several limitations with motion sensors. They can fail when the occupant is not moving, and they do not provide directional information (e.g., whether a person is entering or exiting a room). They also do not provide information on the number of occupants, and the cost of deployment can be high because at least one motion sensor must be installed in each area of interest.